Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C68/00—Preparation of esters of carbonic or haloformic acids
  • C07C68/08—Purification; Separation; Stabilisation

Definitions

• the present invention relates to a method for recovering diphenylcarbonate in substantially pure form from a solution of diphenylcarbonate and phenol. More particularly, the present invention relates to the formation of a crystalline 1:1 molar adduct of diphenylcarbonate and phenol in a solution of diphenylcarbonate and phenol, the isolation of such 1:1 molar adduct from such phenolic solution, and the recovery of diphenylcarbonate therefrom.
• diphenylcarbonate was made by a variety of procedures which resulted in the production of mixtures of diphenylcarbonate and phenol.
• One procedure involves the phosgenation of phenol in an aqueous environment (slurry or melt), or in a solvent such as methylene chloride. After the removal of sodium chloride, the diphenylcarbonate can be separated from residual phenol by vacuum distillation.
• a second route to diphenylcarbonate is by transesterification of dimethylcarbonate with phenol.
• a more direct procedure for making diphenylcarbonate involves the carbonylation of phenol with carbon monoxide.
• a transition metal catalyst such as a palladium catalyst is used in the carbonylation route in combination with a quaternary ammonium halide.
• a further procedure for making diphenylcarbonate involves the reaction between a cycloalkylene carbonate and phenol.
• the carbonylation of phenol can involve the use of a complex palladium catalyst which can include a thermally unstable quaternary ammonium halide which can generate corrosive by-products.
• Reaction by-products such as phenyl salicylate and organic cocatalyst, such as benzoquinone, which can be consumed during the course of the reaction can result in additional impurities in the carbonylation reaction mixture.
• separation of unreacted phenol can be effected by distillation from the reaction mixture, the diphenylcarbonate residue can be contaminated with various catalyst ingredients.
• the present invention is based on the discovery that a single phase mixture ranging from about 20-70% by weight of diphenylcarbonate and about 80-30% by weight of phenol can form a crystalline 1:1 molar diphenylcarbonate-phenol adduct, if allowed to cool to a temperature below 51° C.
• the 1:1 molar crystalline adduct can be separated from the remaining liquid phase. Heating the recovered 1:1 molar crystalline adduct to a temperature of 40°-180° C. at a reduced pressure can provide the separation of phenol by distillation and a substantially pure diphenylcarbonate residue.
• a diphenylcarbonate purification method which comprises,
• adduct crystalline 1:1 molar adduct of diphenylcarbonate and phenol, hereinafter referred to as "adduct"
• a solution of diphenylcarbonate and phenol at temperatures in the range of between about 33° C. to 48° C.
• Such phenol and diphenylcarbonate (DPC) solutions can have an initial DPC content of about 30-60% by weight and can provide an adduct recovery of up to about 70% by weight, or up to 80% by weight of DPC.
• a second crystallization of the adduct from the remaining mother liquor at 37° C. can provide an additional 28% by weight of DPC at an adduct solids level of about 29% by weight.
• the total recovery of DPC from the recovered adduct utilizing standard distillation procedures at temperatures of up to 180° C., and preferably 60° to 120° C., at pressures of 10 torr to 150 torr can therefore be up to 70% by weight of DPC.
• Impurities in the initial phenol DPC mixture can vary depending upon the type of reaction used to form the DPC.
• a solution of phenol and DPC formed during a carbonylation reaction can have such impurities as tetrabutylammonium bromide (TBAB), phenyl salicylate, and a number of side products such as, isomeric biphenols, phenolic ethers and subsequent products resulting from the carbonylation of these compounds.
• TBAB tetrabutylammonium bromide
• phenyl salicylate phenyl salicylate
• side products such as, isomeric biphenols, phenolic ethers and subsequent products resulting from the carbonylation of these compounds.
• a convenient measuring procedure for the degree of contamination is the "rejection factor" which is defined as the mass of the contaminant in the liquid phase divided by the mass of the contaminant in the adduct phase. Accordingly, a minimum acceptable rejection factor might be 4:1, while a mixture having substantially pure adduct or a minimal amount of contamination in the adduct phase would have a substantially higher rejection factor, such as up to 100:1. Contamination of adduct crystals also can be effected with adduct liquid.
• aqueous phenol such as a mixture of 9% water and 91% phenol (liquified phenol) can minimize the loss of DPC by washing the adduct.
• the following example shows the procedure for making diphenyl carbonate utilizing a gas flow reactor.
• the gas flow reactor is capable of delivering in a continuous manner, a mixture of carbon monoxide and oxygen maintained at a substantially constant molar ratio and partial pressure.
• the diphenyl carbonate was prepared by a carbonylation reaction using a palladium catalyst, tetrabutylammonium bromide, a cobalt complex containing a pentadentate Schiff base ligand, and terpyridine. The following procedure was employed:
• the reactor was heated to 110° C. over a 15 minute period Stirring was initiated at 540-550 rpm once the reactor temperature reached 40° C. Upon reaching a reactor temperature of 110° C., aliquots were taken periodically for GC analysis in order to quantify the amount of diphenyl carbonate produced. At 0.5 hr, the yield of diphenyl carbonate was 9.79 g (14.26%). At 1.0 hr, the yield of diphenyl carbonate was 16.2 g (23.6%). At 2.0 hr, the yield of diphenyl carbonate was 23.1 g (33.7%). After the two hour sample was taken, the reaction mixture was cooled at 60° C., and depressurized to atmospheric pressure.
• the combined reaction mixtures were then allowed to cool to 40° C. which resulted in the separation of a DPC/phenol adduct.
• the DPC/phenol adduct was recovered from the reaction mixture by vacuum filtration resulting in the recovery of 58.5 g of the adduct representing a 74% yield.
• the DPC/phenol adduct was then heated to a temperature of 120° C. at a pressure of 80 torr to effect the distillation of phenol which resulted in the recovery of about 33.4 g of diphenyl carbonate.
• a mixture of 50 grams of phenol and 50 grams of diphenylcarbonate at 80° C. was cooled to 45° C., then maintained at 45° C. for 1 hour.
• a mixture having about 30% solids was produced.
• a diphenylcarbonate/phenol adduct was recovered by filtration. There was obtained, 30.2 grams of adduct which provided 21 grams of diphenylcarbonate upon phenol distillation.

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• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)

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Citations (4)

• 1992
  • 1992-08-17 US US07/929,860 patent/US5239106A/en not_active Expired - Lifetime
• 1993
  • 1993-08-11 ES ES93306331T patent/ES2108826T3/es not_active Expired - Lifetime
  • 1993-08-11 EP EP93306331A patent/EP0583936B1/de not_active Expired - Lifetime
  • 1993-08-11 DE DE69315011T patent/DE69315011T2/de not_active Expired - Lifetime
  • 1993-08-17 JP JP5203055A patent/JP2752570B2/ja not_active Expired - Fee Related

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